Manufacture of cements from calcium sulphate and blast furnace slag



106. COMPOSHIONS.

COATING R PLASTC 9 '2 Patented July 1, 1941 UNITED STATES PATENT OFFICEMANUFACTURE OF CEMIENTS FROM CAL- CIUM SULPHA'IE AND BLAST FURNACE SLAGJohn Stanley Dunn, Billingham-on-Tees, and Victor Leiebnre, London,England, assignors to Imperial Chemical Industries Limited, acorporation of Great Britain No Drawing. Application February 23, 1939,Se-

iilsNo. 257,817. In Great Britain February 22,

(Granted under the provisions of sec- 14, act of March 2, 1927; 357 O.G.

8 Claims.

This invention relates to cements obtained from glcium sulphate andgranulated blast furwater-settingsnrcpenties, especial! when mixed T {2with an exciter such as an alkalihate, or M both. The exciter chiefly usfese cement-s C ,4 is Portland cement clinker. which liberates limeduring 5 mg.

p ithecementsthemselves, particularly in the tensile strength prevailingduring the early stagm of setting.

According to the present invention, therefore,

we add to a cement comprising bl urnace slag,

and w? roducin exciter, a sm propo on, e. g.

per c""ent'. 5y weig' ht, of one or more aluminate of calc umqof a mamcontain- 12 age same. The ven me e o ecsormassesmadefrom thesaidcements. In ca in out the invention we preferably employ cements of thekind described and claimed in Dunn et a1 U.. S. application Serial No.257,816, namely, cements comprising blastiurnace slag, calcium sulphateand a limebfitaining orilime producing excitery in which at least 60 percent. of the slag particles, at least 50 per cent. of the exciterparticles, and at least 60 K per cent. of the final mixed cementparticles, are of diameter not exceeding 30 microns. As the alcium sulhate constituent of the cement we prefer to employ natural anh 'te andas the esciter Portland cement c er we give:

i (a) sulgho-aluminates of calcium, obtained for examp e y e ac on o eum sulphate on calm aluminatg solutions, wEereBy compounds of t eformulae 309.0%. C8504.

.12H2O may Ob ed.

(b) the product obtained by reacting ground granulated blast furnace slcalcium sulphate and me, E the presence of water.

(c) ground set or partially set cement mac from granule ed blast urnaces ag, lcium sulhate and a e-con-tai 19' roducw, e. g. rt an cement er. gsetting sulp'n'o-afiminafis of calare Preferably these substances areadded in a finely divided condition, 1. e. such as will pass a 170 meshB. S. S. sieve. Material in coarser form. e. g. that just passing a 50B. S. B. sieve may also be used.

To illustrate the benefits derived from employing the said additions wegive the following example:

A cement was made containing 85 parts by weight of ground granulatedblast furnace slag. 15 parts any dri-te and 5 parts P03 land cement. Totwo separate portions of t s cement were added 2%% and 5% respectivelyoi. the solids formed in the interaction of blast furnace as.

gypsum and lime water. The tensile strengtEi of Tensile stemgth bs-I 1.in

Percentage of modifier added 1 setting As many apparently widelydifferent embodiments of this invention may be made without departingfrom the spirit and scope thereof, it is to be understood that theinvention is not limited to the specific embodiments thereof, except asdefined in the appended claims.

We claim:

1. A water-setting cement comprising granulated blast furnace slag.calcium sulphate and a lime-containing or 1ime-producing exciter, towhich has been added before setting of said cement a small proportion ofone or more sulphualuminates of calcium or of a material containing thesame to increase the tensile strength of said cement in the early stagesof setting.

2. A cement according to claim 1 in which at least per cent. of the slagparticles, at least 50 per cent. of the exciter particles, and at least60 per cent. of the cement mixture to which the Examinersulpho-aluminates are added are of diameter not exceeding 30 microns.

3. A cement according to claim 1, in which the calcium sulphateconstituent of the cement is natural anhydrite.

4. A cement according to claim 1, in which the exciter is Portlandcement clinker.

5. A cement according to claim 1, in which the sulpho-aluminates areadded in finely divided condition, 1. e. such as will pass a 170 mesh B.S. S. sieve.

6. A cement according to claim 1, in which the proportion of addedsulpho-aluminates or material containing the same is 1-5 per cent. by

weight of the cement.

I. A cement according to claim 1, in which the calcium sulphateconstituent is natural anhydrite and in which the exciter is Portlandcement clinker.

8. A water-setting cement of the type comprising granulated blastfurnace slag, calcium suiphate and a lime-containing or lime-producingexciter, to which has been added before setting of said cement toincrease the tensile strength thereof in the early stages of setting asmall pro portion of ground already set cement of the said type.

JOHN STANLEY DUNN. VICTOR LEFEBURE.

